LEEDpat is designed to help interpret experimentally observed LEED spot
patterns for well-ordered surfaces especially in the presence of
superlattices. In particular, LEEDpat allows one to tell which 2D surface
lattices are compatible with an observed LEED pattern. Rotational domains and
glide plane extinction of spots are taken into account (the latter at normal
incidence only). For further details see
LEEDpat manual

LEEDpat also provides extensive 2D symmetry information, showing all
rotational, mirror and glide symmetries that are compatible with the observed
pattern. This allows the user to narrow down possible structural models of
the surface and to propose atomic positions in the actual structure. However,
LEEDpat does not itself predict structural models or atomic
coordinates: it does not calculate spot intensities, which would be needed to
determine atomic positions.

The user can select any basic 2D substrate lattice (square, hexagonal,
rectangular, or oblique), including any possible symmetries (i.e. any of the
17 two-dimensional space groups). The user can also specify any commensurate
or incommensurate superlattice, again with any possible symmetries
(commensurate only). LEEDpat then draws both a real-space lattice and a LEED
pattern (representing reciprocal lattices), including the option of
symmetry-related domain orientations (of equal weight). The user can thus, by
trial and error, find the pattern that best matches the experiment.

Version 4 of LEEDpat includes many improvements and new
features. In particular, it offers now

Analyses of incommensurate periodic overlayers

Extended handling of hexagonal lattices

Analyses of higher order coincidence (HOC) overlayers

PostScript print output for documentation purposes

ASCII file in/output for session start and archiving

A structure file stack for quick comparisons

Improved visualization of the structure / pattern graphics

Simulation of channel plate geometry in pattern output

Html based help (default for Windows 7 and later)

The present version 4.2 of LEEDpat has some general limitations (which
cannot be overcome) and simplifications (which may be fixed in later
versions):

A direct conversion from observed pattern to real-space lattice is not
possible, due to such frequently-present complications as: mixed structures,
defects, two- and three-dimensional disorder, faceting, ordered steps,
differently oriented terraces, multiple and thermal diffuse scattering, in
addition to the ambiguities due to symmetry-related domains of different
orientation and unequal weights.

Commensurate, incommensurate, and higher-order coincidence
superlattices are allowed in LEEDpat, i.e. the matrices defining
superlattices can have both integer, real, and fractional valued elements. For
incommensurate superlattices symmetry considerations are taken into account
only with respect to the basic 2D lattice (domain formation). The less
user-friendly program SARCH (freely available)
can account for general symmetry of incommensurate superlattices.

Stepped ("vicinal") surfaces produce well-known "spot
splittings". The apparent spot splitting is an intensity effect: only a few
of many spots are intense enough to be visible. LEEDpat will simulate such a
pattern, but will treat all spots as being of equal intensity, thus not
giving the appearance of "split spots". The program SARCH (freely available), does
include kinematic LEED intensities and can be used to simulate this "spot
splitting" effect.

Despite these limitations, LEEDpat can simulate a large fraction of observed
patterns, and thus should be useful in most cases.

Start downloading the LEEDpat package in a single file (3 MB) by
identifying yourself with your name and email address.(This information will be used ONLY for announcements of major updates
and not passed on to others. Obviously fake or obscene addresses will not be accepted.)

Your name

Your e-mail address

To complete downloading click the download button.

After having downloaded file LEEDpat42Install.exe you may install LEEDpat on
your PC. For instructions see INSTALLATION on this
page. You may return to this page from the download page by clicking the
"RETURN TO LEEDpat homepage" button in the download page.

The INSTALLATION of LEEDpat is straightforward and consists in the
most general case of four steps. (Note that your browser may have
download switches set such that one or more of the following steps are
performed automatically.)

Unpack all files by running the downloaded file
LEEDpat42Install.exe. (Your browser may use a default directory for
file downloading. Then you may have to look for this file in your PC
with Window's find option.) This will ask you for the name of an
installation subdirectory, e.g. c:\TEMP (or any other temporary
directory, which must be different from the permanent directory where
you wish LEEDpat to be installed). This subdirectory contains all
system installation files. Note that the installation directory
cannot be used as the final LEEDpat directory, see step 2.

Install all LEEDpat files by running Setup.exe inside the
installation subdirectory (see step 1). This will ask you for the name
of the final LEEDpat subdirectory, e.g. c:\Program files\LEEDpat42 (or
any other permanent directory), to contain the LEEDpat package.

Set a LEEDpat icon on the desktop. Go to directory INSTALL and
create a shortcut of LEEDpat42.exe (open directory INSTALL with your
file explorer, right-click file LEEDpat42.exe, choose "Create Shortcut"
from the menu which creates a shortcut file) and drag the shortcut file
onto the desktop.

Clean up by removing all installation files from directory TEMP.
You may leave the original download file LEEDpat42Install.exe for
backup purposes.

NOTE that starting with version 4.2 of LEEDpat the new html based help
option (default for MS Windows 7 and later) is available by default but the
traditional Windows help can still be used as an option. Microsoft, in its wisdom, has
discontinued providing the traditional Windows help engine (WinHlp32.exe)
with MS Windows 7 and later by default. The absence of
WinHlp32.exe in your PC will make the old LEEDpat help option unavailable.
However, WinHlp32.exe can be downloaded from Microsoft
and installed in your Windows PC free of charge. This will enable the traditional
LEEDpat help option if needed.

NOTE that Microsoft does not include the Visual Basic 6 runtime
environment (required by LEEDpat) in its Windows 8, 8.1 versions by default.
However, the VB6 runtime environment can be downloaded from Microsoft
and installed in your Windows PC free of charge.
This will enable LEEDpat to run also under Windows 8, 8.1.

You RUN LEEDpat

from the Windows program selection:
choose "Start | Programs | LEEDpat42 | LEEDpat42" from the taskbar.

from the Windows desktop:
double-click at the LEEDpat icon of the desktop. This requires a
LEEDpat icon to exist on the desktop, see step 3 of the installation.

from the Windows command line:
choose "Start | Run..." from the taskbar; type
"\$rundir$\LEEDpat42.exe" where $rundir$ denotes the directory path where
you installed LEEDpat (e.g. c:\Program files\LEEDpat42) and press "enter".